The big V8 residing within the nose of the new, 2004 Audi S4 produces awesome sensations: 334 bhp will do that. Powerful and refined, the S4 also sports an exhaust note that's never before been heard from an Audi, and that reportedly became a source of contention among Audi's top brass. Word has it the S4's engineers anticipated that the exhaust's extremely aggressive sound would upset conservative senior management, who would move to quiet the S4 before it was signed off for production. So instead of previewing the S4 as they envisioned it, the designers purposely gave it an exceptionally loud voice. "Great car, but let's make it a tad less randy sounding," said management (or words to that effect).

The engineers countered with the exhaust they originally built. It was a typical "offer-counteroffer" corporate negotiation but showed some pretty clever thinking from engineering. Still, one has to wonder how the much anticipated RS4 will sound with its twin turbos. Turbos offer some degree of sound abatement, and we'd hate to see its growl subdued in any way.

While the instantaneous gratification of the new S4's big motor is obvious, the ballistic characteristics of a turbocharged engine are part of what made the first S4 so good. I'm not yet ready to cast it aside for something new, and neither are people like Chris Clark, as demonstrated by his 2002 S4.

That the 2.7-liter twin-turbo V6 is a tuneable chunk of metal has already been well documented. Basic mods such as slightly larger turbos, a better exhaust, a free-flow intake system and more boost all conspire to wring considerably more power from the mill. Clark, however, followed a decidedly different path by hooking up with Don Istook, a laid-back Texan with extensive motorsport experience. Istook has been involved in racing since 1971, winning eight regional and national SCCA amateur titles in his division. In 1984, he began to compete professionally in IMSA, running in numerous 24-, 12-, 6- and 3-hour races, including the 24 Hours of Daytona, Watkins Glen, Mid-Ohio and the 12 Hours of Sebring.

Istook has maintained numerous Porsches, including 911s, 924s, (SSA and DP), 944s and a Carrera GTR. He has also run Toyota Supra Turbos, Audi Quattros, Pontiacs, Firebirds and Camaros. Recently Istook and Bob Aines formed the Istook/Aines Motorsport Group to compete in the Speedvision World Challenge series and the Motorola Cup, campaigning an S4.

Which brings us to the Audi on these pages.

Clark has no intention of racing his car, but he did want it to be a fast and reliable daily driver. Typically you visit a race shop to go fast--the reliable part (and a huge chunk of dough) leaves after winning the first race. "Originally I intended to go with the AWE Stage III program," recalled Clark. "Don was pretty confident the package would deliver what I was looking for, and he was all set to do the installation."

As fate would have it, a pair of new race-prepped Audi 2.7t motors showed up on Istook's doorstep. Don thought one of them might make a better candidate for the job. Though largely stock, one of the engines had been enlarged to 2.8 liters and fitted with slightly larger Audi Motorsport pistons. Clark took a look at the engine and pointed to his Audi.

"Let's put that in there," he said.
While the engine was on the stand, Istook went to work, augmenting the mill with stuff from Audi's RS parts bin. The heads were replaced with RS4 units, featuring ports some 30% larger than a standard S4, supplemented with higher-flow RS4 fuel injectors and an RS4 fuel pump. The intake manifold, modular mass airflow housing, bi-pipe, and y-pipe are RS4 parts as well. For improved breathing, the RS4's K04 turbochargers and bigger intercoolers were used in conjunction with a fully custom stainless-steel exhaust.

"The exhaust is key to making the S4 perform," said Istook. "We made this system by hand, using 2.5- and 3.5-in. mandrel-bent tubing and high-flow resonators and mufflers. For the record, I don't have a jig to mass-produce this exhaust. It's a time-consuming piece to fabricate, and I don't think it's repeatable on a predetermined template."

An RS4 clutch and oil cooler found their way into the mix, as did AWE's nicely designed drivetrain stabilizer, a neat piece that keeps the transmission from unwanted movement during hard launches.

The car was also fitted with Istook Racing's snub mounts and (wisely) Stoptech's big brakes and Audi S8 rear calipers and rotors.

Istook was pleased with the way things were progressing and was confident this engine could withstand years of hard usage. "The S4's bottom end, with its multi-bolt main, is extremely durable," explained Istook. "We can get more than 20 races from these things without rebuilding them. You wouldn't get near that longevity or durability with a normally aspirated Audi 2.8-liter V6. Don't even try," he added.

With considerably more potential than a standard S4, it was obvious the ECU would need a substantially uprated mindset. Calls went out to MTM, AMS, APR and finally GIAC, which agreed to custom-program the ECU on its awd dynamometer. GIAC was one of the first chip tuners to wring more power from Audi's new breed of force-fed engines, and it has compiled data on hundreds of cars in stock trim. Straight from the assembly line, a stock S4 was shown to produce 171 whp and 211 lb-ft of torque. With the driveline loss computations, those numbers are just about right. But before placing Clark's S4 on the dyno, GIAC chose to swap out the Bosch air mass sensor for a more reliable Hitachi unit from AWE. After a week's work and well over 100 pulls, Clark's Audi revealed a dramatic increase to 348 whp and 346 lb-ft of twist--on lousy 91-octane California-spec fuel! (It should be noted that the accompanying dyno chart/run was performed on a cold vs.cold car. A more accurate, real-world methodology would include repeating the test while the car was hot. Heat tends to be a great deflator of big dyno numbers.)

Further modifications included H&R coilovers for better handling, and grip was enhanced with 8x18-in. O.Z. Superleggera wheels shod with Yokohama Parada Spec-2 radials, measuring 225/40ZR-18.

Andrew at GIAC gave us a call and described the Audi as a "must-drive" vehicle, especially as Clark was taking the car back home to Texas. On a deserted stretch of road, I planted my right foot and tried to keep it in a straight line. The first impression was this was quite possibly one of the quickest and most refined S4s I had driven. Unlike some modified S4s, this beast did not run out of steam as the tach rose well past 6500 rpm. Power came on strongly around 1700 rpm, and at about 2700 rpm it pinned me back in the seat. I hit 120 mph in an insanely short span and made full use of the big, four-piston Stoptech binders. Clearance issues made the twisted sections difficult, as there was significant tire rubbing within the wheelwells; moreover, Clark was on the brink of evacuating himself from both ends.

"Oy, mate...just let me out...do whatever you want with the car...just let me out first!""

This car was so fast, it nearly scared the crap out of the owner.

I can only imagine what Clark spent on this beast, but the result seems well worth it. Like a great many S4 fans, Clark's quest for more performance appears insatiable, and he wants to share the enthusiasm with fellow Audi fans.

Therefore, in late August of 2003, european car will hold an Audi S4 challenge. If you think your S4 has what it takes to endure The Streets of Willow Springs and a dyno day, drop us a line. Clark is first on the list.

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